PROJECT SUMMARY Despite efforts of prevention and education programs, licit and illicit drug use among pregnant women remains prevalent1. Most drugs of abuse easily cross the placenta and can alter the intricate balance among fetal neurotransmitters and receptors, which critically dictate in utero development of the brain's functional wiring system2-5. Therefore prenatal drug exposures (PDE) have long-lasting implications for brain and behavioral development since a small perturbation to the immature brain circuits may cascade into substantial deviations during long-term growth6. Existing behavioral studies provide converging evidence on the detrimental effects of PDE throughout development 1,6,7 but mechanistic studies of the brain basis of PDE remains scarce, especially during the infancy period. Nevertheless, studying the brain mechanisms of PDE during infancy is critical and urgently needed given that: 1) the infancy period immediately follows PDE insults and features the most dynamic postnatal brain development; 2) the infancy period is least confounded by postnatal environmental adversities that frequently accompany PDE; 3) identification of brain alterations associated with PDE during this stage has the best potential to guide early preventive intervention before behavioral problems onset. Our previous results8,9 demonstrated significant and widespread functional connectivity alterations in neonates prenatally exposed to cocaine and marijuana, respectively. However, three major areas need to be better delineated: 1) an overall picture of PDE effects on whole brain functional organization is lacking; 2) a more systematic delineation of the potential differential drug effects and their interactions is needed given the multi- drug exposure for most of the drug-abusing mothers; 3) the prediction power of detected neonatal functional alterations for later behavioral outcomes remains to be determined. Our long-term goal is to derive early functional-connectivity-based brain biomarkers for different PDEs that will reliably predict long-term behavioral outcomes. Our goal in this project is to derive neonate-based functional connectivity signatures for different PDEs and test their prediction power for 3-month behavioral outcomes. This project is significant because it is expected to be the first to identify drug-specific neurophenotypes for different PDEs on early brain functional and behavioral development, prior to the damaging postnatal influences that may accompany parental drug abuse. It is innovative because: 1) It will integrate resting-state brain functional connectivity and cognitive and behavioral function to quantify the potential drug-specific and drug-common effects on brain and behavior development in neonates; 2) It will apply detailed multi-level whole brain survey to discern differential drug-effect profiles and leverage advanced machine learning algorithms to better characterize their link with later behavioral outcomes. It is relevant to public health because it will provide currently unavailable knowledge of PDE effects on developing brain functional networks in neonates and inform earlier interventions that are documented to be most effective before symptom onset.